Skewed volumetric data with OpenGL glTexture3D with different texture dimensions - c++

Question

I have a problem to figure out how to correctly use glTexImage3D when width, height and depth are different values.
I've thought that in order to avoid 3 new on triple pointers and then be very careful to delete everything, boost::multiarray could have been very useful, so I've used.
boost::multi_array<GLubyte, 3> texture3DVolume;
texture3DVolume.resize(boost::extents[textureSizeX][textureSizeY][textureSizeZ]);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glGenTextures(1, &(this->textureID));
glBindTexture(GL_TEXTURE_3D, this->textureID);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MAG_FILTER, GL_LINEAR_MIPMAP_LINEAR);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glEnable(GL_TEXTURE_3D);
glTexImage3D(GL_TEXTURE_3D, 0, GL_LUMINANCE, this->textureSizeX,this->textureSizeY, this->textureSizeZ, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, texture3DVolume.data());
int textureSizeX=512;
int textureSizeY=512
int textureSizeZ=511;
with 511 I get a skewed texture. The texture coordinates are made with a very simple shader, for every vertex (the vertices of a [-0.5,0.5]x[-0.5,0.5]x[-0.5,0.5] cube) I use:
// vertex shader...
texture_coordinate = (v.xyz+vec3(1.0))*0.5;
// then in the fragment shader
gl_FragColor = texture(my_color_texture, texture_coordinate);
but my result is skewed. I really don't know if I have a problem on how the data are laid out with boost::multiarray or what...
My result is the following:
As you see the spheres are skewed and this is because the width==height but they are !=depth. I would like to better understand if this is a problem of how the data are laid out and/or strides.
If I set depth=512 I get the correctly proportioned cube.

Answer 1

I've thought that in order to avoid 3 new on triple pointers and then be very careful to delete everything, boost::multiarray could have been very useful, so I've used.
Either is wrong. A 3 stage new-ed array is actually a tree. It's an array of pointers to arrays of pointers to values. What you want is a flat region of data. Don't bother with multidimensional arrays, because you don't know how those arrange the data internally.
Use a simple 1-dimensional array of length width * height * depth. Also make sure you set the right GL_UNPACK_ALIGNMENT, usually 1.